JPS6195592A - Integrated distribution bragg's reflection type semiconductor laser - Google Patents

Abstract

PURPOSE:To control the oscillating wavelength in a stable uniaxial mode state in the range of several Angstrom by forming an active region, a phase control region and a DBR region, and forming a control electrode also on the DBR region. CONSTITUTION:An active region 1, a phase control region 2 and a DBR region 3 are formed, and a control electrode 20 is formed on the DBR regions. Thus, the wavelength range of approx. several Angstrom is varied substantially in a stable uniaxial mode operation state by altering the control current. Further, the oscillating spectral beam width at the uniaxial mode oscillation time also depends upon the control state, and the oscillating spectral beam width of 4MH2 is obtained by setting to the most stable state. For example, the length of the region 2 is 300mum, the length of the region 3 is 150mum and the length of the region is 150mum, thereby varying the wavelength of 45Angstrom by implanting a current of approx. 60mA.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser whose oscillation wavelength can be controlled.

(Prior art and its problems) A distributed feedback semiconductor laser (DPB-LD) that exhibits stable single-axis mode operation even during ultra-high-speed modulation at the Gb/s level;
Distributed black reflective semiconductor lasers (DBR-LDs) are seen as promising light sources for long-distance, high-capacity optical fiber communications. Having four people develop a wavelength control mechanism for these semiconductor lasers, which have good single-axis mode properties, will be useful not only for the current long-distance, high-capacity direct transmission system, but also for future optical heterodyne communications,
It is expected to be applied to fields such as high-density wavelength division multiplexing transmission, and is considered to be extremely useful. For example, Tomori et al.
.

Lett, 19 (1983), pp 656
) We have developed a direct-coupled integrated DBR-LD that can control the oscillation wavelength as reported in J.C. As shown in Figure 2, Tomori et al. have developed an integrated DBR capable of controlling total loss wavelength, with an active region 1 in the center of the device, a DBRB region 2 on one side, and a phase control region 3 on the other side.
- By making a prototype LD and injecting a current of 4 mA into the phase control region 3, a change in the oscillation wavelength of 4 μm degree was realized. FIG. 3 is for illustrating its operating principle. Third
The horizontal axis of the figure shows wavelength, and the vertical axis shows reflection loss that provides threshold gain. That is, a low value on the vertical axis indicates that the vertical reflection loss is small, and therefore the threshold gain is small and the axis mode is likely to oscillate. Wavelength control integration D by Tomori et al.
In the B-LD, the reflection loss curve shown in FIG. 3 does not change, and each axis mode moves on this curve. The point of each axis mode is determined by the intersection of the phase curve determined by the DB control region 2 and the phase curve determined by the active region 1 and the phase control region 3.By injecting current into the phase control region 3, the latter Since the phase curves change and therefore the fulcrums of the two phase curves change (this causes the oscillation wavelength to change).

? For example, if there are axial modes such as 31, 32, 33, and 34 as shown in FIG. 3 when no current is injected, 32 modes with the smallest reflection loss oscillate at first. By injecting a current into the phase control region, each axial mode given by the fulcrum of the phase curve moves in the direction of the arrow, and the oscillation wavelength changes to the shorter wavelength side. When a certain amount of current is injected, the reflection losses between the 32nd mode and the 33rd mode are reversed, causing a mode jump, and each mode now oscillates. From now on, we will show the wavelength change of the same wavelength. However, in this case (in this case, the reflection loss curve does not change, the black wavelength that gives the lowest threshold gain does not change, i.e., the control wavelength range is determined by the axial mode spacing, and realistic device dimensions cannot be determined. If you think about it, it will only require a few people at most.If we consider future applications such as high-density wavelength division multiplexing optical communications, it will require dozens of people to control the wavelength.At the same time, fine tuning will also be necessary. .

(Objective of the Invention) From the above-mentioned viewpoint, the object of the present invention is to provide an integrated DBR-LD with a novel structure that allows fine tuning of the oscillation mode at the same time as wavelength control on the order of several tens of λ.

(Structure of the Invention) According to the structure of the present invention, an integrated distribution black reflection type medium 4-body laser has at least an active layer on a semiconductor substrate, and has an energy gap larger than that of the active layer, and has diffraction on one surface. and a guide layer in which a grating is formed, at least an active region having the active layer, a phase control region transparent to laser light, and a DBRB region having at least the guide layer are arranged in the laser coaxial direction. One end surface of the n, r+"b active dome formed in a chain becomes a reflective end surface, and two independent grades are formed on the upper part of the Poe's laminated structure, one of which spans the two regions. It is characterized by the fact that it is formed.

(Function/principle of invention) The integrated DBR-LD according to the present invention has an active region.

Phase TiU (1'D region, DJ3fl region are formed,
At least two independent electrodes are formed. DBR
Due to the carrier injection I into the B region, the black wavelength itself shown in FIG. 3 changes. At the same time, the oscillation wavelength of each axial mode can also be changed by injecting carriers into the phase control region. In the former case, a black wavelength change on the order of tens can be realized, and in the latter case, a smooth wavelength change on the order of several tens can be achieved.
For example, when forming the same polarization in those two regions, 2
By appropriately setting the length of each region, it becomes possible to almost completely cover a wavelength range on the order of several tens.

(Example) The present invention will be described in more detail below using drawings showing examples.

FIG. 1 is a schematic cross-sectional view of an integrated distribution black reflective semiconductor laser which is an embodiment of the present invention. To fabricate such an element, first, a diffraction grating 12 is partially formed on an InP substrate 11, and then a diffraction grating 12 with a wavelength of, for example, 1 or 3 μm is formed on the entire surface of the InP substrate 11.
I n o, 7z Ga IIL2. A
s o, 5iP03. A light guide layer 13 and the like were laminated. After that, selective etching and selective epitaxial growth are performed to grow, for example, In with a wavelength of 1.55 μm.6. Ga
o4. As, 9°Po,.

The active layer 14 and the like were laminated so that light was directly coupled, and formed into a buried structure for the purpose of transverse mode control and current confinement. Two monopoles were formed as shown in the subsequent chapters. The control electrode 20 is common to the phase control region 3 and the DB control region 2. By setting the length of each region appropriately, it is possible to oscillate over several tens of wavelength ranges, and mode jumps occur even if the wavelength does not change continuously over all wavelength ranges. It is possible to realize a continuous wavelength change of about several A even when there is no current. - For example, if the phase change of the DB area area 2 is about the same as the active area 1,
If the phase change is approximately twice the amount of the phase change in the portion consisting of the cape region 3 and force), a continuous wavelength change will occur over a wavelength region that is approximately half or more of the total wavelength change including mode jumps. Therefore, it is possible to perform wavelength tuning that is sufficient for application to FSK heterodyne optical communication systems and the like.

In this example, the length of the DBRB region 2 is 300 μm, the length of the small phase control region 3 is 150 μm, and the length of the active region 1 is 815 μm.
By setting it to 0 μm, a wavelength change of 45 A could be achieved by injecting a current f of about 5 QmA. The operation was somewhat unstable in the range of about 4A before and after the axial mode skipping occurred, but in the other wavelength range the axial mode selection ratio was 39d.
Wavelength control was possible under good single-axis mode operation of B or better. Even in the temperature changing CW operation, when current was injected into only the active region 1, a threshold current of 4 QmA and a differential efficiency of about 15 cm were obtained with good reproducibility. In terms of optical output, a stable single-axis mode total loss of up to 10 rnW from the output end face 4 on the active region 1 side was obtained. control fii20
is common to the DBB-region 2 and the phase control region 3; however, only the DBRB region 2 may be made independent, and a common pole may be formed in the active region 1 and the phase control region 3. Good wavelength control can be achieved using just the poles. The phase condition is determined by the combined length of the active region 1 and the phase control region 3,
The intersection point of the DBR vertical phase curve determines the oscillation wavelength of each relaxation mode, so by appropriately setting the length of each region and the injected current, it is possible to
Wavelength control becomes possible within a range of approximately 0A.

In the example IC of the present invention, an active region 12, a phase control region 2, a DBAB region 3 were formed, and a DBRB region 3I and a control '1 pole 20 were formed. By changing the control current, we were able to change a wavelength range of several tens of wavelengths in a nearly stable single-axis mode operation. Furthermore, the oscillation spectrum linewidth during single-axis mode oscillation also depends on the control state, and by setting it to the most stable state, 4 M
Emission spectral linewidths in Hz were obtained.

In the example of the present invention, the refractive index was changed using the plasma effect of carriers caused by current injection I, and the wavelength was controlled. In Example F, the semiconductor material used may also be used for purposes such as changing the refractive index.
A material with a wavelength of 1 μm, including P as a substrate and InGaAsP as an active layer and a light guide layer, was used, but the material is not limited to this.
, GaAgAs.

Other semiconductor materials such as InGaAJP and GaAsSb may also be used. In the example, DB
A light guide layer 1 having the same composition in the RB region 2 and the phase control region 3
3 was used, but these may be crystals of different compositions, and etching grooves may be formed between independent electrodes to improve electrical insulation, or a proton irradiation high-resistance layer may be formed. It's okay.

(Effects of the Invention) A feature of the present invention is that in the integrated DBR-I, D, an active region two-phase control region and a DBR region are formed, and a control electrode is also formed on the DBR region.

This Iζ has made it possible to control the oscillation wavelength in a stable single-axis mode state over a range of several tens of people. Furthermore, it is also possible to control the oscillation spectrum linewidth, which is important in optical heterodyne communication.

We can expect great development as a light source for future high-grade optical fiber communications such as high-density wavelength division multiplexing communications.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic cross-sectional views of an integrated DBR-LD that is an embodiment of the present invention and a conventional integrated DBB-LD, respectively, and Figure 3 is a seven-wavelength DBR reflection loss to illustrate the operating principle. In the figure, 1 is the active region and 2 is the DBR.
, area, and 3 is the phase control area. 4 is an output end face, 11 is an InP substrate, 12 is a diffraction grating, 1
3 is a light guide layer, 14 is an active layer, 20 it fffi
The # electrodes 31, 32, 33, and 34 represent the oscillation axis modes, respectively. Yoshion Patent Attorney Uchihara πl''. Figure 1 Figure 2

Claims (1)

[Claims] A laminated structure having, on a semiconductor substrate, at least an active layer and a guide layer having a larger energy gap than the active layer and having a diffraction grating formed on one surface, an active region having at least the active layer, and a laser. A phase control region transparent to light, a DBR region having at least the guide layer, is formed in a manner extending in the laser resonance axis direction,
One end face of the active region becomes a reflective end face, and two independent electrodes are formed on the upper part of the laminated structure, one of which is a reflective end face.
1. An integrated distributed black reflective semiconductor laser characterized in that one electrode is formed across two regions.